Final: Nitrogen Metabolism II
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13 terms
Terms | Definitions |
|---|---|
 What is related to nitrogen metabolism and arises from very simple starting compounds? | Nucleotide biosynthesis. Two of the nitrogens of purines come from the amine of glutamine; one comes from incorporation of glycine, and one from aspartate. |
| Why is the synthesis of nucleotides carefully balanced in cells? | Imbalances in quantity of nucleoteides is a factor in causing mutations. |
| What types of phosphates in purine nucleotides inhibit synthesis? | Mono, di, and triphosphates. |
| T/F: IMP is not intermediate that is at the branch point between synthesis of AMP and GMP. | False it is an |
| List some ways in which a cell "balances" the control of purine levels. | AMP requires GTP for energy. AMP also inhibits its own synthesis by feedback inhibition. Synthesis of GMP requires ATP for energy and GMP feedback inhibits its own synthesis as well. |
| What do specific kinases, such as AMP kinase, convert? | Nucleoside monophosphates (such as AMP) to nucleoside diphosphates (such as ADP). |
| What converts Nucloside diphosphates to nucleoside triphosphates? | These are catalyzed by nucleoside diphosphokinase (NDPK). NDPK also converts all of the deoxyribonucleoside diphosphates to corresponding deoxyribonucleoside triphosphates. |
| T/F: PUrine breakdown (catabolism) goes through the intermediate Xanthine, which is broken down to uric acid and ultimately to glyoxylate and urea. | True. Also, Uirc acid crystals are the causes of the painful disease known as gout. |
| What is the primary regulatory enxypme of pyrimidine biosynthesis? | ATCase. It provides balance between purines and pyrimidines, since it is activated by a purine (ATP) and inactivated by a pyrimidine (CTP). |
| Amino acides are precursors to what? | Prymidine synthesis. The first prymidine nucleotide made up is UMP, and from it UDP, UTP, and CTP are made. |
| T/F: Deoxyribonucleotides (the building blocks of DNA) are not made up from ribonucleotides (building blocks of RNA_ using the enzyme ribonucleotide reductase (RNR). | False. Note that the precursor ribonucleotides are DIPHOSPHATES and that the reaction simple reduces the hydroxyl group on the ribose ring to a hydrogen, thus making deoxyribose as the sugar on a deoxyribonucleotide. |
| Thymidine nucleotides are made from what? | Uridine nucleotides. |
| List the process that forms Hymidine nucleotides. | UDP goes to dUDP. Then, several reactions later, dTTP is made. |
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